Enhanced electrolytic degradation of controlled electrolytic material

ABSTRACT

A method for degrading a downhole article includes exposing the downhole article to a composition comprising a corrosive agent selected from a reducing sugar, ester, aminocarboxylic acid, or a combination thereof. The method also includes contacting the downhole article with the corrosive agent to degrade the downhole article. Additionally, a composition for degrading a downhole article includes water, salt, and a corrosive agent selected from a reducing sugar, ester, aminocarboxylic acid, or a combination thereof.

BACKGROUND

Oil and natural gas wells often utilize borehole components or toolsthat, due to their function, are only required to have limited servicelives that are considerably less than the service life of the well.After a component or tool service function is complete, the downholecomponent or tool must be removed or disposed of in order to recover theoriginal size of the fluid pathway for use, including hydrocarbonproduction, CO₂ sequestration, etc. Disposal of components or tools hasconventionally been done by milling or drilling the component or toolout of the borehole, which is generally a time consuming and expensiveoperation.

In order to eliminate the need for the milling or drilling operation,the removal of components or tools by dissolution of degradable materialusing various borehole fluids has been proposed. The degradablematerials that have been proposed include certain degradable metalalloys formed from reactive metals, such as aluminum, together withother alloy constituents, such as gallium, indium, bismuth, tin, andmixtures and combinations thereof. These materials may be formed bymelting powders of the constituents and then solidifying the melt toform the alloy. They may also be formed using powder metallurgy bypressing, compacting, sintering and the like a powder mixture of areactive metal and other alloy constituent in the various amounts. Todegrade the metal alloys, and thus effectively remove the component ortool from the borehole, strong mineral acids or brine has been used.However, the corrosion rate of mineral acids may be too fast while thecorrosion rate brine may be too slow under downhole conditions.

Advances that avoid the above noted problems would be well received inthe art.

BRIEF DESCRIPTION

Disclosed herein is a method for degrading a downhole article,comprising: exposing the downhole article to a composition comprising acorrosive agent selected from a reducing sugar, ester, aminocarboxylicacid, or a combination thereof; and contacting the downhole article withthe corrosive agent to degrade the downhole article.

Also disclosed is a method for degrading a downhole article, comprising:introducing a composition comprising a reducing sugar, ester,aminocarboxylic acid, or combination thereof into a borehole; andremoving, by the composition, a metal from the downhole article todegrade the downhole article.

Further disclosed is a composition for degrading a downhole article,comprising: water; salt; and a corrosive agent selected from a reducingsugar, ester, aminocarboxylic acid, or a combination thereof.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedmethod is presented herein by way of exemplification and not limitation.

The inventor has discovered that a corrosive agent such as a reducingsugar, ester, and aminocarboxylic acid selectively and controllablydegrades a downhole article containing certain electrolytic materials sothat the downhole article will no longer substantially block or impede apassage or fluid flow in a borehole. Moreover, such degradation by thecorrosive agent can expose a surface or feature of a downhole articlethat was previously covered or protected by a material including anelectrolytic material, and the newly exposed surface or feature canprovide a benefit for operating in the downhole environment. Further,the inventor has discovered that such degradation of the downholearticle can be controlled over time. The corrosion agent isenvironmentally benign and is corrosive to electrolytic materials over alarge temperature range where other compounds are either too corrosive(for example, mineral acids such as hydrochloric acid) or not corrosiveenough (for example, brine solutions). These corrosive agents bridge thegap between the corrosion strengths of strong and mild corrosives, suchas hydrochloric acid and sodium chloride aqueous solutions.

According to an embodiment, a degradable downhole article, such as apacker, ball seat, frac plug, proppant, or cement includes anelectrolytic material, which dissolves in a corrosive environment. Suchelectrolytic material is referred to herein as controlled electrolyticmaterial (CEM). The controlled electrolytic material, which is discussedfurther below, can be an electrolytic metal such as described in U.S.patent application Ser. No. 13/194,271, the content of which isincorporated herein by reference in its entirety. Removal of theelectrolytic material from the downhole article causes degradation ofthe downhole article.

In an embodiment, a method for degrading a downhole controlledelectrolytic material (CEM) article includes exposing the downhole CEMarticle to a composition that comprises a corrosive agent and contactingthe downhole article with the corrosive agent to degrade the downholeCEM article. The corrosive agent can be a reducing sugar, ester,aminocarboxylic acid, or a combination thereof.

The downhole CEM article comprises a metal selected from Group 2, Group3, Group 4, Group 5, Group 6, Group 7, Group 8, Group 9, Group 10, Group11, Group 12, Group 13, lanthanoid series, actinoid series of theperiodic table, or a combination thereof. In an embodiment, the metalis, aluminum (Al), calcium (Ca), cobalt (Co), copper (Cu), chromium(Cr), gallium (Ga), indium, (In), iron (Fe), magnesium (Mg), manganese(Mn), molybdenum (Mo), nickel (Ni), palladium (Pd), tungsten (W),silicon (Si), silver (Ag), tin (Sn), titanium, (Ti), vanadium (V),yttrium (Y), zinc (Zn), zirconium (Zr), an alloy thereof, or acombination thereof. It is believed that these metals can be used in adownhole environment and can be corroded by the corrosive agent.

Additionally, the downhole CEM article can include other corrodiblemetals, metal oxides, composites, soluble glasses, and the like. Usefulcorrodible materials dissolve under an aqueous condition. According toan embodiment, alloying or trace elements can be included in varyingamounts to adjust the corrosion rate of the metal. For example, four ofthese elements (cadmium, calcium, silver, and zinc) have tomild-to-moderate accelerating effects on corrosion rates, whereas fourothers (copper, cobalt, iron, and nickel) have a still greater effect oncorrosion. Commercial magnesium alloys, which include differentcombinations of the above alloying elements, can achieve differentcorrosion rates and include (although not limited to), for example,those alloyed with aluminum, strontium, and manganese such as AJ62,AJ50x, AJ51x, and AJ52x alloys, and those alloyed with aluminum, zinc,and manganese such as AZ91A-E alloys.

It will be appreciated that alloys having corrosion rates greater thanthose of the above exemplary alloys are contemplated as being usefulherein. For example, nickel has been found to be useful in decreasingthe corrosion resistance (i.e., increasing the corrosion rate) ofmagnesium alloys when included in small amounts (i.e., less than 1% byweight). In an embodiment, the nickel content of a magnesium alloy isless than or equal to about 0.5 wt. %, specifically less than or equalto about 0.4 wt. %, and more specifically less than or equal to about0.3 wt. %, to provide a useful corrosion rate for the corrodibledownhole article. In an exemplary embodiment, magnesium particles arealloyed with about 0.25 wt. % Ni. Similar ranges are applicable to othermetal alloys disclosed herein.

The above alloys are useful as a metal in the downhole article and areformed into the desired shape and size by casting, forging, machining,or a combination thereof. Alternatively, powders of the metal or themetal alloy are useful for forming part of the downhole article or thepowder form of CEM can be used Such metal or metal alloy powders canhave a particle size of from about 0.5 micrometers (μm) to about 400 μm,and more specifically about 10 μm to about 250 μm. The powder can befurther coated using a method such as chemical vapor deposition,anodization or the like, or admixed by physical method suchcryo-milling, ball milling, or the like, with a metal or metal oxidesuch as Al, Ni, W, Co, Cu, Fe, oxides of one of these metals, or thelike. Such coated metal powders are examples of controlled electrolyticmaterial (CEM). The CEM material can be molded or compressed into thedesired shape by, for example, cold compression using an isostatic pressat about 40 kilopound per square inch (kpsi) to about 80 kpsi (about 275megapascal (MPa) to about 550 MPa), followed by forging or sintering andmachining, to provide a desired shape and dimension. Alternatively, themetallic powder comprised of a core and coating may be used withoutfurther processing.

It will be understood that the metal, including CEM, will thus have anycorrosion rate necessary to achieve the desired performance of thedownhole article. In an embodiment, the metal (e.g., CEM material) usedin the downhole article has a corrosion rate of about 0.01 mg/cm²/hourto about 20 mg/cm²/hour, specifically about 0.1 mg/cm²/hour to about 15mg/cm²/hour in, for example, an aqueous 3 wt. % KCl solution (based onthe weight of the solution) at 200° F. (93° C.) and even higher in thecorrosive agents disclosed herein. The corrosion rate can be adapted tobe below these ranges for a particular application of the downholearticle.

In an embodiment, degrading the downhole article comprises reducing themetal in the downhole article by the corrosive agent or a product of thecorrosive agent. Particularly, the corrosive agent is the reducingsugar, and reducing the metal in the downhole article comprisesoxidizing the reducing sugar. Alternatively, the corrosive agent is theester. In this latter case, reducing the metal in the downhole articlecomprises hydrolyzing the ester to produce an organic acid and oxidizingthe organic acid with concomitant reduction of the metal in the downholearticle.

In a further embodiment, degrading the downhole article comprisesleaching the metal from the downhole article by the corrosive agent or aproduct of the corrosive agent. Here, the corrosive agent is theaminocarboxylic acid. The method also includes chelating, by theaminocarboxylic acid, the metal which was leached from the downholearticle.

In an embodiment, the reducing sugar comprises a monosaccharide,disaccharide, oligosaccharide, polysaccharide, a derivative thereof, ora combination thereof. Particularly, the reducing sugar can be analdose, ulosonic acid, ketose, ulronic acid, or a combination thereof.More particularly, examples of the reducing sugar includeglyceraldehyde, erythrose, threose, ribose, arabinose, xylose, lyxose,allose, altrose, glucose, mannose, gulose, idose, galactose, talose,dihydroxyacetone, erythrulose, ribulose, xylulose, psicose, fructose,sorbose, tagatose, glucoronic acid, galacturonic acid, cellobiose,maltose, lactose, melibiose, maltulose, lactulose, isomaltose,laminaribiose, maltotriose, a derivative thereof, or a combinationthereof.

As used herein, the term “monosaccharide” refers to a polyhydroxyaldehyde H—[CHOH]_(a)—CHO or polyhydroxy ketone H—[CHOH]_(b)—CO—[CHOH]—Hwith a, b, and c being independently three or more carbon atoms,specifically a, b, and c being independently about 3 to about 50, andmore specifically a, b, and c being independently about 3 to about 25.“Monosaccharide” (as opposed to an oligosaccharide or polysaccharide)denotes a single unit, without glycosidic connection to other suchunits. In an embodiment, the monosaccharide includes an aldose,dialdose, aldoketose, ketose, diketose, deoxy sugar, amino sugar, andtheir derivatives, provided that the parent compound has a (potential)carbonyl group. As used herein, “aldose” refers to a monosaccharide withan aldehydic carbonyl or potential aldehydic carbonyl group. As usedherein, “ketose” refers to a ketonic carbonyl or potential ketoniccarbonyl group. As used herein, the term “potential aldehydic carbonylgroup” refers to the hemiacetal group arising from ring closure of themonosaccharide. Likewise, as used herein, the term “potential ketoniccarbonyl group” refers to the hemiketal structure. As used herein,“dialdose”” refers to a monosaccharide containing two (potential)aldehydic carbonyl groups. As used herein, “diketose” refers to amonosaccharide containing two (potential) ketonic carbonyl groups. Asused herein, “ketoaldose” refers to a monosaccharide containing a(potential) aldehydic group and a (potential) ketonic group. It is notedthat use of parenthesis around the word “potential” indicates that thegroup may be present or potentially present in the reducing sugar. Asused herein, “deoxy sugar” refers to a monosaccharide in which analcoholic hydroxy group has been replaced by a hydrogen atom, except atthe anomeric carbon. As used herein, “amino sugar” refers to amonosaccharide in which an alcoholic hydroxy group has been replaced byan amino group. As used herein, “uronic acid” refers to a monocarboxylicacid derived from an aldose by replacement of the CH₂OH group with acarboxy group. As used herein, “ulosonic acid” refers to a carboxylicacid derived from a ketose by replacement of the C1-hydroxyl group witha carboxy group.

As discussed above, the reducing sugar can be a monosaccharide,disaccharide, oligosaccharide, polysaccharide, or a combination thereof,including derivatives thereof. The disaccharide, oligosaccharide,polysaccharide, and their derivatives have a reducing sugar end group.Further, both the D- and L-stereoisomers of the reducing sugar can beemployed herein.

The reducing sugar can be a straight chain, cyclic configuration, or acombination thereof. In general, a temperature-dependent equilibriumexists between the straight and cyclic configurations of the reducingsugar. As will be appreciated by one skilled in the art, as the straightchain form of a reducing sugar is oxidized during the reduction of themetal in the downhole article, more straight chain form is produced fromthe cyclic form of the reducing sugar in accordance with Le Chatelier'sprinciple.

The reducing sugar can be substituted if such substituted reducing sugardoes not adversely interfere with removal of the metal from the downholearticle. As used herein, the term “substituted reducing sugar” refers toa reducing sugar in which one or more hydrogen atoms in hydroxyl groupsof the reducing sugar, other than the carbonyl carbon that is to bereduced in concert with reduction of the metal in the downhole article,are replaced by various functional groups. Examples of substitutedreducing sugars include phosphate-containing reducing sugars such asribose-5-phosphate, ribose-3-phosphate, arabinose5-phosphate,arabinose-3-phosphate, glyceraldehyde-3phosphate, andarabinose-3,5-diphosphate; acetylated reducing sugars such as3,5-di-O-acetyl-D-ribose; and 5-O-benzoyl-D-arabinose. Examples offunctional groups include phosphate, acetyl, hydrogen, alkyl, alkoxy,fluoroalkyl, cycloalkyl, heterocycloalkyl, cycloalkyloxy, aryl, aralkyl,aryloxy, aralkyloxy, heteroaryl, heteroaralkyl, alkenyl, alkynyl, NH₂,amine, alkyleneamine, aryleneamine, alkenyleneamine, and a combinationthereof.

The amount of the reducing sugar in the composition is that amountrequired to sufficiently reduce the metal in the downhole article, thusdegrading the downhole article. Factors including the exposure time, theconcentration of other ingredients in the composition, volumetric flowrate at the downhole article, and the formation temperature as well asother considerations known to those skilled in the art may guide thedecision of the amount of the reducing sugar to include in thecomposition. In an embodiment, the reducing sugar is present in thecomposition in an amount from about 0.1 weight percent (wt. %) to about50 wt. %, specifically from about 0.2 wt. % to about 30 wt. %, and morespecifically about 0.5 wt. % to about 25 wt. %, based on the weight ofthe composition.

In an embodiment, the corrosive agent is the ester. The ester hydrolyzesto produce an organic acid. The organic acid can decrease the pH of thecomposition proximate to the downhole article. Without wishing to bebound by theory, it is believed that reduction of the pH in the downholeenvironment by the organic acid can aid reductive removal of the metalfrom the downhole article. In this way, the downhole article may bedegraded by the ester.

According to an embodiment, the ester is any ester that produces anorganic acid that interacts with metal in the downhole article todegrade the downhole article. More particularly, degradation of thedownhole article occurs by reduction of the metal by the organic acidproduced by the ester, for example by hydrolysis of the ester. The estercan be a C2 to C32 ester, a derivative thereof, or a combinationthereof. Examples of a C2 to C4 ester include methyl formate, methylacetate, ethyl formate, dimethyl carbonate, vinyl acetate, methylacrylate, propylene carbonate, dimethyl oxalate, ethyl acetate,isopropyl formate, methyl propanoate, and propyl formate.

Examples of C5 and C6 esters include ethyl acrylate, methylmethacrylate, vinyl propanoate, dimethyl malonate, butyl formate, ethylpropanoate, isopropyl acetate, methyl butyrate, methyl isobutyrate,2-methylpropyl formate, propyl acetate, diethyl carbonate,2-methoxyethyl acetate, 2-ethoxyethyl acetate, dimethyl maleate,1-methyl-2-propenyl acetate, ethyl acetoacetate, diethyl oxalate,dimethyl succinate, 1,1-ethanediol diacetate, 1,2-ethanediol diacetate,butyl acetate, sec-butyl acetate, tert-butyl acetate, ethyl butyrate,ethyl isobutyrate, isobutyl acetate, isopentyl formate, methyltrimethylacetate, methyl valerate, pentyl formate, propyl propanoate,and 2-ethoxyethanol acetate.

Examples of C7 to C9 esters include butyl propanoate, ethyl isovalerate,ethyl 2-methylbutyrate, ethyl trimethylacetate, ethyl valerate, formicacid hexyl ester, isobutyl propanoate, isopentyl acetate, isopropylbutyrate, 1-methylbutyl acetate, methyl hexanoate, pentyl acetate,propyl butyrate, butyl lactate, 3-methoxybutyl acetate, benzyl formate,methyl benzoate, phenyl acetate, methyl salicylate, diethyl maleate,butyl methacrylate, cyclohexyl acetate, isobutyl methacrylate,2,3-butanediol diacetate, diethyl methylmalonate, diethyl succinate,dimethyl adipate, butyl butyrate, butyl isobutyrate, ethylbutyl acetate,ethyl hexanoate, heptyl formate, 2-hexanol acetate, hexyl acetate,sec-hexyl acetate, isobutyl isobutyrate, isopentyl propanoate, methylheptanoate, pentyl propanoate, benzyl acetate, ethyl benzoate, ethylsalicylate, 1,2,3-propanetriol triacetate, cyclohexyl propionate,diethyl glutarate, butyl valerate, ethyl heptylate, heptyl acetate,hexyl propanoate, isopentyl butanoate, methyl caprylate, octyl formate,and pentyl butyrate.

Examples of C10 to C32 esters include triethylcitrate, dimethylphthalate, cyclohexyl butyrate, diethyl adipate, ethylene glycoldibutyrate, ethyl caprylate, 2-ethylhexyl acetate, hexyl butyrate, hexylisobutyrate, nonyl formate, methyl nonanoate, octyl acetate,butoxyethoxyethyl acetate, diethyl heptanedioate, ethyl nonanoate,heptyl butyrate, isononyl acetate, methyl decanoate, ethyl decanoate,and 1-ascorbyl palmitate.

In a specific embodiment, the ester is ethyl acetate, 2-ethoxyethylacetate, ethyl acetoacetate, triethylcitrate, methyl benzoate, dimethylphthalate, a derivative thereof, or a combination thereof.

The amount of ester used is that amount required to reduce the metal inthe downhole article. As with the reducing sugar, the amount of theester used depends on factors such as the injection time desired, theconcentration of other ingredients in the composition, volumetric flowrate at the downhole article, formation temperature, and other factors.The ester is preferably present in the composition in an amount fromabout 0.1 weight percent (wt. %) to about 40 wt. %, specifically fromabout 0.2 wt. % to about 20 wt. %, and more specifically about 0.5 wt. %to about 15 wt. %, based on the weight of the composition.

In an embodiment, a low molecular weight ester is used. Generally, thehigher the molecular weight of the ester, the less water soluble theester. As a result, lower molecular weight esters may be more convenientand/or more efficacious to use. The molecular weight of the ester can befrom about 60 g/mol to about 1000 g/mol, specifically about 60 g/mol toabout 500 g/mol, and more specifically about 60 g/mol to about 300g/mol.

As discussed above, the corrosive agent can be the aminocarboxylic acid.In an embodiment, degrading the downhole article comprises leaching themetal from the downhole article by the corrosive agent or a product ofthe corrosive agent. Here, the corrosive agent is the aminocarboxylicacid that leaches and/or chelates the leached metal from the downholearticle.

In an embodiment, the aminocarboxylic acid is a C1 to C35 and N1 to N10aminocarboxylic acid. Examples of the aminocarboxylic acid includediethylenetriaminepentaacetic acid (DTPA); ethylenediaminetetraaceticacid (EDTA); ethylene-bis(oxyethylenenitrilo)tetraacetic acid (EGTA);N,N′-di(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid (HBED);(hydroxyethyl)ethylenediaminetriacetic acid (HEDTA); iminodiacetic acid(IDA); nitrilotriacetic acid (NTA); a derivative thereof; a saltthereof; or a combination thereof. Salts of the aminocarboxylic acidinclude, for example, calcium disodium EDTA, diammonium EDTA,dipotassium EDTA, disodium EDTA, triethanolamine salt of EDTA(TEA-EDTA), tetrasodium EDTA, tripotassium EDTA, trisodium EDTA, andtrisodium HEDTA.

In a specific embodiment, the aminocarboxylic acid is EDTA, Na₄EDTA,(NH₄)₂H₂EDTA, NTA, Na₃NTA, HEDTA, Na₃HEDTA, DTPA, K₅DTPA, a derivativethereof, or a combination thereof and the like.

The amount of aminocarboxylic acid used is that amount required to leachand/or chelate the metal in the downhole article. As with the reducingsugar, the amount of the aminocarboxylic acid used depends on factorssuch as the injection time desired, concentration of other ingredientsin the composition, volumetric flow rate at the downhole article,formation temperature, and other factors. The aminocarboxylic acid ispreferably present in the composition in an amount from about 0.1 wt. %to about 40 wt. %, specifically from about 0.2 wt. % to about 30 wt. %,and more specifically about 0.5 wt. % to about 20 wt. %, based on theweight of the composition.

In an embodiment, the aminocarboxylic acid has a leaching rate of themetal in the downhole article from about 0.1 mg/hour to about 2000mg/hour, specifically about 1 mg/hour to about 1000 mg/hour, and morespecifically about 10 mg/hour to about 500 mg/hour.

In another embodiment, a method for degrading a downhole articlecomprises introducing a composition comprising a reducing sugar, ester,aminocarboxylic acid, or combination thereof into a borehole; andremoving, by the composition, a metal from the downhole article todegrade the downhole article. The method further comprises oxidizing thereducing sugar, wherein removing the metal comprises reducing the metalin the downhole article by the reducing sugar. In another embodiment,the method further comprises hydrolyzing the ester to an organic acid;and adjusting, with the organic acid, the pH of the borehole proximateto the downhole article to a pH from about 2 to about 8, morespecifically about 3 to about 7, and more specifically about 4 to about6. According to an embodiment, removing the metal from the downholearticle comprises leaching the metal from the downhole article by theaminocarboxylic acid; and chelating the metal by the aminocarboxylicacid.

In an embodiment, the composition described above includes water, salt,a corrosive agent, optionally surfactant, optionally solvent, or acombination thereof.

In an embodiment, the composition includes water or brine. The selectionof the water and salanity of the brine can depend on a desired densityfor the composition. In an embodiment, the water or brine is present inthe composition in an amount from about 1 wt. % to about 99 wt. %,specifically about 10 wt. % to about 90 wt. %, and more specificallyabout 20 wt. % to about 80 wt. %.

Brine can be included in the foregoing compositions to modify thedensity of the composition as well as moderate the corrosion rate of themetal in the downhole article. In an embodiment, the salt in the brineis NaCl, KCl, NaBr, MgCl₂, CaCl₂, CaBr₂, ZnBr₂, NH₄Cl, sodium formate,cesium formate, and the like. The salt can be present in the compositionin an amount from about 0.5 wt. % to about 50 wt. %, specifically about1 wt. % to about 40 wt. %, and more specifically about 1 wt. % to about25 wt. %, based on the weight of the composition.

The surfactant can be anionic, cationic, zwitterionic, or non-ionic. Thesurfactant can be present in the composition in an amount from about0.05 wt. % to about 50 wt. %, specifically about 0.1 wt. % to about 40wt. %, and more specifically about 1 wt. % to about 25 wt. %, based onthe weight of the composition.

The solvent is not particularly limited as long as the corrosive agentis miscible therein to an appreciable extent. In an embodiment, thesolvent can contain oxygen and be, for example, an alcohol, glycol,ether, pyrrolidone, and the like. The solvent can be present in thecomposition in an amount from about 0.05 wt. % to about 90 wt. %,specifically about 0.1 wt. % to about 80 wt. %, and more specificallyabout 1 wt. % to about 50 wt. %, based on the weight of the composition.

In a specific embodiment, the composition includes about 20 wt. %fructose, based on the weight of the composition. In another embodiment,the composition includes about 2 wt. % CaBr₂ and about 10 wt. % glucose,based on the weight of the composition. In another embodiment, thecomposition includes about 0.6 wt. % ethyl acetoacetate, based on theweight of the composition. Alternatively, the composition includes about15 wt. % (NH₄)₂H₂EDTA, based on the weight of the composition.Alternatively, the composition includes about 5 wt. % KCl and about 10wt. % K₅DTPA, based on the weight of the composition.

In addition to the corrosion agents discussed above, the composition caninclude an additive. Examples of the additive include mineral acid,additional organic acid, biocide, breaker, clay stabilizer, corrosioninhibitor, crosslinker, friction reducer, gelling agent, iron controlagent, scale inhibitor, additional surfactant, or a combination thereof.Such additives are thought to, for example, facilitate entry into rockformations, kill bacteria and reduce risk of fouling, stabilize clay,provide well maintenance, facilitate proppant entry, improve surfacepressure, provide proppant placement, prevent precipitation, and reducefluid tension of the composition. In an embodiment, the additive ishydrochloric acid, glutaraldehyde, 2,2-dibromo-3-nitrilopropionamide,peroxodisulfates, salt (for example, tetramethylammonium chloride),methanol, potassium hydroxide, sodium acrylate, polyacrylamide, guargum, citric acid, thioglycolic acid, ethylene glycol, polyacrylate,isopropanol, or a combination thereof.

In the above embodiments, the viscosity of the composition can be about1 centipoise (cp) to about 1000 cp, specifically about 1 cp to about 100cp, and more specifically about 1 cp to about 50 cp, as measured, forexample, by a Brookfield viscometer. Additionally, in some embodiments,the time for degradation of the downhole article by the corrosive agentis from about 0.1 hours to about 300 hours, specifically about 0.1 hoursto about 100 hours, and more specifically about 0.1 hours to about 48hours. Degradation of the downhole article according to embodimentsdiscussed above can occur at a temperature of about 20° C. to about 200°C., specifically about 30° C. to about 175° C., and more specificallyabout 35° C. to about 150° C.

In some embodiments, the downhole article is a downhole tool. Examplesof downhole tools include a packer element, a blowout preventer element,an O-ring, a T-ring, a gasket, a sucker rod seal, a pump shaft seal, atube seal, a valve seal, a seal for an electrical component, aninsulator for an electrical component, a seal for a drilling motor, aseal for a drilling bit, or other downhole elements. According to anembodiment, the downhole article is a component, for example, a ball orball seat in a valve, flapper valve, or plunger in a solenoid. In yetanother embodiment, the downhole article is a degradable metallicparticle such as a proppant, which either totally degrades to be removedor degrades partially to be left as a porous structural element. In aparticular embodiment, the downhole article is a proppant particle mixedwith conventional proppant that is oxidized by a reducing agent toprovide an enhanced porous media after removal of the oxidized metallicparticles, and the pores therein allow increased fluid to flow throughthe proppant pack. Such downhole tools, components, and articles containcontrolled electrolytic material (CEM) material and are degradable withrespect to the reducing agents herein.

While the invention has been described with reference to an exemplaryembodiment or embodiments, it will be understood by those skilled in theart that various changes may be made and equivalents may be substitutedfor elements thereof without departing from the scope of the invention.In addition, many modifications may be made to adapt a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof. Therefore, it is intendedthat the invention not be limited to a particular embodiment disclosed,but that the invention will include all embodiments falling within thescope of the claims. Also, in the drawings and the description, therehave been disclosed exemplary embodiments, and, although specific termsmay have been employed, they are unless otherwise stated used in ageneric and descriptive sense only and not for purposes of limitation,the scope of the invention therefore not being so limited.

All ranges disclosed herein are inclusive of the endpoints, and theendpoints are independently combinable with each other. The suffix “(s)”as used herein is intended to include both the singular and the pluralof the term that it modifies, thereby including at least one of thatterm (e.g., the colorant(s) includes at least one colorant). “Optional”or “optionally” means that the subsequently described event orcircumstance can or cannot occur, and that the description includesinstances where the event occurs and instances where it does not. Asused herein, “combination” is inclusive of blends, mixtures, alloys,reaction products, and the like. All references are incorporated hereinby reference.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. Further, it should further be noted that the terms “first,”“second,” and the like herein do not denote any order, quantity, orimportance, but rather are used to distinguish one element from another.The modifier “about” used in connection with a quantity is inclusive ofthe stated value and has the meaning dictated by the context (e.g., itincludes the degree of error associated with measurement of theparticular quantity).

What is claimed:
 1. A method for degrading a downhole article,comprising: exposing the downhole article to a composition comprising acorrosive agent selected from a reducing sugar; and contacting thedownhole article with the corrosive agent to degrade the downholearticle at a temperature of about 35° C. to about 150° C.; wherein thedownhole article is degraded at a faster rate in the presence of thecorrosive agent as compared to a brine without the corrosive agent; andfurther wherein the downhole article is degraded at a slower rate in thepresence of the corrosive agent as compared to a mineral acid.
 2. Themethod of claim 1, wherein the downhole article comprises a metalselected from Group 2, Group 3, Group 4, Group 5, Group 6, Group 7,Group 8, Group 9, Group 10, Group 11, Group 12, Group 13, lanthanoidseries, actinoid series of the periodic table, or a combination thereof.3. The method of claim 2, wherein the metal is selected from aluminum,calcium, cobalt, copper, chromium, gallium, indium, iron, indium,magnesium, manganese, molybdenum, nickel, nobelium, palladium, scandium,tin, titanium, tungsten, silicon, vanadium, yttrium, zinc, zirconium, ora combination thereof.
 4. The method of claim 3, wherein degrading thedownhole article comprises reducing the metal in the downhole article bythe corrosive agent or a product of the corrosive agent.
 5. The methodof claim 1, wherein reducing the metal in the downhole article comprisesoxidizing the reducing sugar.
 6. The method of claim 5, wherein thereducing sugar comprises a monosaccharide, disaccharide,oligosaccharide, polysaccharide, a derivative thereof, or a combinationthereof.
 7. The method of claim 6, wherein the reducing sugar includesan aldose, ulosonic acid, or a combination thereof.
 8. The method ofclaim 6, wherein the reducing sugar includes a ketose, ulosonic acid,ulronic acid, or a combination thereof.
 9. The method of claim 6,wherein the reducing sugar is selected from glyceraldehyde, erythrose,threose, ribose, arabinose, xylose, lyxose, allose, altrose, glucose,mannose, gulose, idose, galactose, talose, dihydroxyacetone,erythrulose, ribulose, xylulose, psicose, fructose, sorbose, tagatose,glucuronic acid, galacturonic acid, cellobiose, maltose, lactose,melibiose, maltulose, lactulose, isomaltose, laminaribiose maltotriose,derivatives thereof, or a combination thereof.
 10. The method of claim3, wherein degrading the downhole article comprises leaching the metalfrom the downhole article by a product of the corrosive agent.
 11. Themethod of claim 1, wherein the composition is substantially free of acidexcept for the corrosive agent, an acid produced from the corrosiveagent, or a combination thereof.
 12. A method for degrading a downholearticle, comprising: introducing a composition comprising a reducingsugar into a borehole; and removing, by the composition, a metal fromthe downhole article to degrade the downhole article at a temperature ofabout 35° C. to about 150° C.; wherein the downhole article is degradedat a faster rate in the presence of the corrosive agent as compared to abrine without the corrosive agent; and further wherein the downholearticle is degraded at a slower rate in the presence of the corrosiveagent as compared to a mineral acid.
 13. The method of claim 12, furthercomprising oxidizing the reducing sugar, wherein removing the metalcomprises reducing the metal in the downhole article by the reducingsugar.